Arterial blood pressure and carotid baroreflex function during arm and combined arm and leg exercise in humans

Volianitis, Stefanos; Yoshiga, Chie C.; Vogelsang, Thomas; Secher, Niels H.

doi:10.1111/j.1365-201x.2004.01292.x

Cited by 26 publications

(38 citation statements)

References 43 publications

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“…Indeed, cardiopulmonary baroreceptor loading may exert a central inhibitory effect during sympatho-excitatory maneuvers, such as carotid baroreceptor unloading or exercise. However, as cardiopulmonary baroreceptor loading during exercise is strongly associated with an attenuated carotid baroreflex resetting (36,48), it is unlikely that this would explain the age-related relocation of the operating point observed in the present study, as we observed an augmented carotid baroreflex resetting in older individuals. Further studies are needed to determine the mechanisms underlying the age-related attenuation in the BP responses to carotid baroreflex unloading during exercise.…”

Section: Discussioncontrasting

confidence: 42%

Carotid baroreflex control of arterial blood pressure at rest and during dynamic exercise in aging humans

Fisher

Kim²,

Young³

et al. 2010

American Journal of Physiology-Regulatory, Integrative and Comp

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Fisher JP, Kim A, Young CN, Fadel PJ. Carotid baroreflex control of arterial blood pressure at rest and during dynamic exercise in aging humans. Am J Physiol Regul Integr Comp Physiol 299: R1241-R1247, 2010. First published September 8, 2010 doi:10.1152/ajpregu.00462.2010.-The arterial baroreflex is fundamental for evoking and maintaining appropriate cardiovascular adjustments to exercise. We sought to investigate how aging influences carotid baroreflex regulation of blood pressure (BP) during dynamic exercise. BP and heart rate (HR) were continuously recorded at rest and during leg cycling performed at 50% HR reserve in 15 young (22 Ϯ 1 yr) and 11 older (61 Ϯ 2 yr) healthy subjects. Five-second pulses of neck pressure and neck suction from ϩ40 to Ϫ80 Torr were applied to determine the full carotid baroreflex stimulus response curve and examine baroreflex resetting during exercise. Although the maximal gain of the modeled stimulus response curve was similar in both groups at rest and during exercise, in older subjects the operating point (OP) was located further away from the centering point (CP) and toward the reflex threshold, both at rest (OP minus CP; Ϫ10 Ϯ 3 older vs. 0 Ϯ 2 young mmHg, P Ͻ 0.05) and during exercise (OP minus CP; Ϫ10 Ϯ 2 older vs. 1 Ϯ 3 young mmHg, P Ͻ 0.05). In agreement, older subjects demonstrated a reduced BP response to neck pressure (simulated carotid hypotension) and a greater BP response to neck suction (simulated carotid hypertension). In addition, the magnitude of the upward and rightward resetting of the carotid baroreflex-BP stimulus response curve with exercise was ϳ40% greater in older individuals. These data indicate that despite a maintained maximal gain, the ability of the carotid baroreflex to defend against a hypotensive challenge is reduced, whereas responses to hypertensive stimuli are greater with advanced age, both at rest and during exercise. cardiovascular control; autonomic nervous system; baroreflex sensitivity; arterial baroreceptors; total vascular conductance THE ARTERIAL BAROREFLEX (ABR) plays a critical role in the moment-to-moment regulation of arterial blood pressure (BP) via modulation of autonomic neural activity to the heart and vasculature. Although a wealth of data has indicated that aging is associated with impairments in resting cardiac baroreflex function (3,14,19,29), studies examining ABR control of muscle sympathetic nerve activity (SNA) have reported equivocal results demonstrating impaired, preserved, or augmented responsiveness in older healthy adults (11,14,24,29,30,46). Moreover, regarding overall ABR regulation of BP and aging, limited studies have been performed suggesting either reduced (24, 27) or unchanged (4, 41) control with advanced age. Furthermore, to date, the effect of aging on ABR control of BP during dynamic exercise has not been studied. During exercise it has been shown in both animals (1, 8) and young healthy subjects (35, 38) that the ABR continues to regulate BP by resetting to operate around the exercise-induced elevation...

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Section: Discussioncontrasting

confidence: 42%

Carotid baroreflex control of arterial blood pressure at rest and during dynamic exercise in aging humans

Fisher

Kim²,

Young³

et al. 2010

American Journal of Physiology-Regulatory, Integrative and Comp

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“…In resting and exercising humans, increases in CBV can be accomplished by changing the posture from upright to supine (107), by infusion of serum albumin (79,81) or infusion of a blood volume expander, such as low molecular weight dextran, and by increases in pedal frequency, for example, from 60 to 80 rpm at the same oxygen uptake (81). Decreases in CBV during rest and exercise can be accomplished by changing posture from supine to upright (81) and using lower body negative pressure (78,79).…”

Section: Arterial Baroreflexmentioning

confidence: 99%

Neural control of circulation and exercise: a translational approach disclosing interactions between central command, arterial baroreflex, and muscle metaboreflex

Michelini

O’Leary

Raven

et al. 2015

American Journal of Physiology-Heart and Circulatory Physiology

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Michelini LC, O'Leary DS, Raven PB, Nobrega AC. Neural control of circulation and exercise: a translational approach disclosing interactions between central command, arterial baroreflex, and muscle metaboreflex*. Am J Physiol Heart Circ Physiol 309: H381-H392, 2015. First published May 29, 2015; doi:10.1152/ajpheart.00077.2015.-The last 100 years witnessed a rapid and progressive development of the body of knowledge concerning the neural control of the cardiovascular system in health and disease. The understanding of the complexity and the relevance of the neuroregulatory system continues to evolve and as a result raises new questions. The purpose of this review is to articulate results from studies involving experimental models in animals as well as in humans concerning the interaction between the neural mechanisms mediating the hemodynamic responses during exercise. The review describes the arterial baroreflex, the pivotal mechanism controlling mean arterial blood pressure and its fluctuations along with the two main activation mechanisms to exercise: central command (parallel activation of central somatomotor and autonomic descending pathways) and the muscle metaboreflex, the metabolic component of exercise pressor reflex (feedback from ergoreceptors within contracting skeletal muscles). In addition, the role of the cardiopulmonary baroreceptors in modulating the resetting of arterial baroreflex is identified, and the mechanisms in the central nervous system involved with the resetting of baroreflex function during dynamic exercise are also described. Approaching a very relevant clinical condition, the review also presents the concept that the impaired arterial baroreflex function is an integral component of the metaboreflex-mediated exaggerated sympathetic tone in subjects with heart failure. This increased sympathetic activity has a major role in causing the depressed ventricular function observed during submaximal dynamic exercise in these patients. The potential contribution of a metaboreflex arising from respiratory muscles is also considered. autonomic; baroreflex; central command; exercise; metaboreflex THIS ARTICLE is part of a collection on 1st Pan American Congress of Physiological Sciences: Physiology Without Borders. Other articles appearing in this collection, as well as a full archive of all collections, can be found online at http://ajpheart.physiology.org/.A wide range of complex but routine behaviors such as feeding, shivering, locomotion, aggressive/defensive, and sexual behaviors triggers concomitant activation of somatomotor and autonomic outflows (47). Dynamic exercise is a complex physiological challenge involving highly coordinated activity of skeletal muscles, rapid and immediate increases in respiratory function, heart rate (HR), stroke volume and cardiac output associated with changes in regional vascular resistance, and redistribution of systemic blood flow that cause a slight increase in mean blood pressure (108). The increased blood flow to active muscles provides the necessary o...

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“…To avoid this problem, Thr and Sat have been defined as the values of X at which Y is below or above the upper and lower plateau values of Y, respectively, by some arbitrary small value. Very commonly (see, e.g., 12,[17][18][19][20][21][22][23]28), this arbitrary value is taken as 5% of the response range for Y, and we shall follow this convention here.Many authors have used an equation derived by Chen and Chang (2) to calculate Thr and Sat, as follows:It is commonly stated (see, e.g., 12,[17][18][19][20][21][22][23]28) that the values of Thr and Sat calculated according to Eqs. 3 and 4 are the values of X at which the corresponding Y values are 5% (of the response range) below and above the upper and lower plateau values of Y, respectively.…”

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confidence: 99%

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Calculation of threshold and saturation points of sigmoidal baroreflex function curves

McDowall¹,

Dampney²

2006

American Journal of Physiology-Heart and Circulatory Physiology

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McDowall, Lachlan M., and Roger A. L. Dampney. Calculation of threshold and saturation points of sigmoidal baroreflex function curves. Am J Physiol Heart Circ Physiol 291: H2003-H2007, 2006. First published May 19, 2006 doi:10.1152/ajpheart.00219.2006The logistic sigmoid function curve provides an accurate description of the baroreflex input-output relationship and is the most commonly used equation for this purpose. The threshold (Thr) and saturation (Sat) values for the baroreflex are commonly defined as the values of mean arterial pressure (MAP) at which the reflexly controlled variable (e.g., heart rate or sympathetic nerve activity) is within 5% of the upper or lower plateau, respectively, of the sigmoid function. These values are referred to here as Thr 5% and Sat5%. In many studies, Thr and Sat are calculated with the equations Thr ϭ A3 Ϫ 2.0/A2 and Sat ϭ A3 ϩ 2.0/A2, where A3 is the value of MAP at the point where the reflexly controlled variable is at the midpoint of its range and A2 is the gain coefficient. Although it is commonly stated that the values of Thr and Sat calculated with these equations represent Thr 5% and Sat5%, we show here that instead they are significantly greater and less than Thr5% and Sat5%, respectively. Furthermore, the operating range (difference between Thr and Sat) calculated with these equations is 32% less than the difference between Thr5% and Sat5%. We further show that the equations that provide correct values of Thr5% and Sat5% are Thr5% ϭ A3 Ϫ 2.944/A2 and Sat5% ϭ A3 ϩ 2.944/A2. We propose that these be used as the standard equations for calculating threshold and saturation values when a logistic sigmoid function is used to model the open-loop baroreflex function curve. mathematical modeling; input-output relationship; baroreflex operating range; regression analysis THE BARORECEPTOR REFLEX is the major feedback control system regulating arterial blood pressure in the short term (5, 14), and possibly also in the longer term (15,27). Numerous studies in humans and animals have demonstrated that the baroreceptor reflex can be reset under physiological conditions such as exercise (6 -8, 12, 17, 19 -24, 26, 28), sleep (18), heat stress (3), or pregnancy (4) and also pathological conditions such as hypertension (9, 11) and cardiovascular deconditioning (10). To quantify the changes in baroreflex function that occur under different conditions, many investigators have used a mathematical equation to describe the relationship between input [e.g., mean arterial pressure (MAP)] and output (e.g., heart rate or sympathetic nerve activity). In some cases, where the carotid sinus pressure can be controlled independently of systemic arterial pressure, the input is carotid sinus pressure and the output is systemic arterial pressure.Kent et al. (13) first proposed that a logistic sigmoid function curve be used to describe baroreflex function, according to the following equation:where Y is the output (dependent) variable (e.g., heart rate, sympathetic nerve activity, or systemic arterial...

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Arterial blood pressure and carotid baroreflex function during arm and combined arm and leg exercise in humans

Abstract: These findings demonstrate that during combined arm and leg and exercise in the upright position the CBR resets to a lower blood pressure than during arm cranking likely because the central blood volume is enhanced by the muscle pump of the legs.

Cited by 26 publications

References 43 publications

Carotid baroreflex control of arterial blood pressure at rest and during dynamic exercise in aging humans

Carotid baroreflex control of arterial blood pressure at rest and during dynamic exercise in aging humans

Neural control of circulation and exercise: a translational approach disclosing interactions between central command, arterial baroreflex, and muscle metaboreflex

Calculation of threshold and saturation points of sigmoidal baroreflex function curves

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